1. Field
Example embodiments relate to solar cells and methods for fabricating the same.
2. Description of the Related Art
Conventionally, a p-n junction is used not only as a diode for rectifying operations but also for opto-electronic devices (e.g., solar cells, light emitting diodes (LEDs), and image sensors). When fabricating p-n junctions for general-use single-layered solar cells, silicon (Si) is used as the host material, and phosphorous (P) and boron (B) may be added as n-type and p-type doping materials, respectively. However, a single-layered solar cell is disadvantageous, because it has low efficiency.
The efficiency of a solar cell is affected by the band gap (Eg) of the host material. For example, a solar cell with a host material having a large band gap is inefficient, because it cannot absorb light having energy smaller than the band gap. In contrast, a solar cell with a host material having a small band gap is also inefficient, because (although it can absorb light having energy larger than the band gap) the surplus energy beyond the band gap is lost as heat. Of the host materials used in single-layered solar cells, CdTe has the highest efficiency of 31%, but this is still relatively low.
Because sunlight has a broad range of wavelengths, a host material capable of absorbing the broad range of wavelengths is required to effectively utilize sunlight as a source of electrical energy. A large-sized, high-efficiency solar cell may be attained by forming a high-quality p-n junction on a glass substrate. However, a high temperature of 1000° C. or more is typically required to form a high-quality p-n junction. For this reason, the substrate used to form the high-quality p-n junction is restricted to relatively expensive substrates (e.g., silicon wafer, Al2O3, SiC). Accordingly, there is increased difficulty and costs associated with the manufacture of large-sized p-n junctions and large-sized solar cells.